Abstract
Permanent magnet synchronous machines (PMSMs) operation above base speed is typically achieved by injecting negative d -axis current to produce flux weakening. However, this mode of operation increases copper, stator/rotor core, and permanent magnet (PM) losses, penalizing the efficiency and increasing the risk of demagnetization. Variable flux PMSMs in which PMs are magnetized/demagnetized during normal operation of the machine have been proposed to avoid the use of flux weakening current. However, PM aging due to magnetization/demagnetization cycles has not been thoroughly studied yet. This article analyzes the variation of NdFeB, SmCo, and AlNiCo PMs properties, including magnetic, electric, and thermal, resulting from magnetization/demagnetization cycles.
Highlights
Operation of electric drives using Permanent magnet synchronous machines (PMSMs), both interior PMSMs (IPMSMs) and surface PMSMs (SPMSMs) machines, can be especially challenging for applications in which the machine must operate at high speed, due to the need to inject negative current in the d-axis, known as field weakening current [1]
The increase of the estimated permanent magnet (PM) HF resistance is consistent with the results shown in Figs. 10 to 14, as PM high frequency resistance is a reliable indicator of the PM magnetization state (MS) [23]
Aging effects of the PM used in Variable Flux PMSMs (VF-PMSM) (i.e. NdFeB, SmCo and AlNiCo) due to magnetization/demagnetization cycles have been analyzed in this paper
Summary
Operation of electric drives using PMSM, both interior PMSMs (IPMSMs) and surface PMSMs (SPMSMs) machines, can be especially challenging for applications in which the machine must operate at high speed, due to the need to inject negative current in the d-axis, known as field weakening current [1]. To avoid the injection of flux weakening current and its subsequent adverse effects, variable flux PMSMs (VFPMSM, called memory motors) have been developed. In this type of machines, the PMs magnetization state (MS) is dynamically changed during high speed operation to reduce the needs of flux weakening current [4], [5]. This paper analyzes aging effects on PM magnetic, electric and thermal properties, due to magnetization /demagnetization cycles for PMs used in VF-PMSMs (i.e. NdFeB, SmCo and AlNiCo) [15].
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