Flux Intensifying Feature of Permanent Magnet Assisted Synchronous Reluctance Motor with High Torque Density

Abstract

This paper investigates the flux intensifying (FI) feature of permanent magnet assisted synchronous reluctance motor (PMa-SynRM) in order to achieve high torque density with a small amount of permanent magnet (PM). This motor is thus denoted “FI-PMa-SynRM”. The performance of the developed FI-PMa-SynRM is compared with that of two other counterparts, i.e., an inset surface permanent magnet synchronous motor (SPMSM) and a synchronous reluctance motor (SynRM) to highlight the strengths of the FI-PMa-SynRM. In addition, an analysis on partial demagnetization and torque density of the developed FI-PMa-SynRM is conducted to demonstrate its advantages. The finite element method (FEM) is employed for the analysis in terms of flux linkage and inductances so that the effectiveness of the FI characteristics is validated. The analysis shows that a high torque density (24.79 Nm/L or even greater) can be achieved with a small amount of PM (0.72% motor volume). The ability of anti-demagnetization is also fulfilled. Furthermore, experimental results are provided to validate the analysis findings.

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“…The other disadvantage is that fluid-shaped flux barriers cannot accommodate standardised, "off-the-shelf" ferrite magnets [187,188], making the magnets' manufacturing more complicated and costly. [131] and (c) FI-PMASynRM [194] topologies.…”

“…Flux-Intensifying Permanent Magnet-Assisted Synchronous Reluctance Machines (FI-PMASynRMs) were recently proposed [194][195][196], offering a solution for reducing the irreversible demagnetisation of ferrite magnets. This topology involves placing permanent magnets on the surface of the rotor in the d-axis instead of the q-axis in the flux barriers.…”

“…This approach has been shown to offer enhanced output torque and reduced torque ripple with a limited amount of permanent magnets, helping to avoid irreversible demagnetisation, especially in flux-weakening operation [195]. Furthermore, the FI-PMASynRM maintains its saliency ratio regardless of the increasing current, unlike a SynRM [194]. In [194], a comparison of an SPMSM, a SynRM, and an FI-PMASynRM is presented.…”

“…Furthermore, the FI-PMASynRM maintains its saliency ratio regardless of the increasing current, unlike a SynRM [194]. In [194], a comparison of an SPMSM, a SynRM, and an FI-PMASynRM is presented. In terms of torque production, FI-PMASynRM (15.95 Nm) is ahead of the SynRM (8.65 Nm) by 84.4% and SPMSM (11.93 Nm) by 33.7%.…”

“…Figure12. A 2D cross-section of (a) SynRM[131], (b) PMASynRM[131] and (c) FI-PMASynRM[194] topologies.…”