Abstract
For the analysis of the process of partial demagnetization of permanent magnets (PMs) in electric machines, a field model of coupled electromagnetic and thermal phenomena was proposed. In the proposed approach the non-linearity of the magnetic circuit, the effect of temperature on the magnetic, electrical and thermal properties of the materials as well as the developed method for modeling the process of partial demagnetization of the PMs were taken into account. In order to verify the usefulness and effectiveness of the developed algorithm as well as software for analyzing the impact of temperature and the process of partial demagnetization of the magnets on the operation of a PM motor, the results of calculations were compared with the results of experimental studies. The experimental tests were carried out on a specially designed and constructed measuring test stand. The results of the research on the process of partial demagnetization of magnets in the line start permanent magnet synchronous motor (LSPMSM) are presented and the conclusions resulting therefrom have been formulated.
Highlights
A N IMPORTANT disadvantage of electric machines excited by permanent magnets is the possibility of deterioration of their operational parameters by irreversible reduction of the main magnetic flux [1]
This irreversible reduction of the magnetic flux may be caused by partial demagnetization of the permanent magnets
In the studies on the partial demagnetization process of permanent magnets (PMs), to determine the magnetic fields which cause irreversible demagnetization of the magnets in electric machines the approaches based on simplified equivalent circuits [18], [22] as well as the finite element method [23], [24], [27], are used
Summary
A N IMPORTANT disadvantage of electric machines excited by permanent magnets is the possibility of deterioration of their operational parameters by irreversible reduction of the main magnetic flux [1] The value of this magnetic flux has an impact, among others on the electromagnetic torque generated in the machine, the electromotive force induced in the machine windings and efficiency of the machine [2]–[5]. Several heat sources can be identified in electrical motors They cause power losses dissipated in windings, in magnetic circuits and in bearings [2], [13]–[16]. The accumulation of adverse thermal exposures can cause a large increase in the temperature of magnets and, as a consequence, lead to their partial demagnetization by the impact of armature magnetomotive force. The research on the comprehensive analysis of the process of partial demagnetization of the magnets and minimization of its impact on functional parameters of motors are carried out in many scientific centers around the world [2], [4], [6]–[8], [18]
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