Design framework for magnet loss reduction in permanent magnet synchronous machines

Thusara Samith Sirimanna, Sirimanna Withanage Don

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https://hdl.handle.net/2142/122236 Copy

Description

Title

Design framework for magnet loss reduction in permanent magnet synchronous machines

Author(s)

Thusara Samith Sirimanna, Sirimanna Withanage Don

Issue Date

2023-11-27

Director of Research (if dissertation) or Advisor (if thesis)

Haran, Kiruba

Doctoral Committee Chair(s)

Haran, Kiruba

Committee Member(s)

• Stillwell, Andrew
• Jin, Jianming
• Miljkovic, Nenad

Department of Study

Electrical & Computer Eng

Discipline

Electrical & Computer Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• magnet eddy-currents
• segmentation
• loss validation
• harmonic loss
• loss reduction framework

Abstract

The permanent magnet synchronous motor has become the most attractive option in high power density motor applications, including electric vehicles and electric aircraft propulsion. Compared to other motor topologies, the difference of PMSM is in rotor construction, where the rotor field is obtained from permanent magnets without external excitation. Although rotor losses are smaller in magnitude compared to stator losses, lack of active cooling could make the rotor losses a significant challenge to rotor thermal management and could potentially demagnetize the permanent magnets. Most common NdFeB magnets are metallic, which induce magnet eddy currents when operated under stator magnetic field, due to both space and time harmonics. Available analytical magnet loss models operate under assumptions on eddy current reaction field, field uniformity, and segmentation. Many 2D models that can capture slot harmonics do not include the reaction field while the models that can capture reaction field do not capture the field nonuniformity. Part of this work extends the available travelling wave model for SPM time harmonic losses to accurately capture the slot harmonic losses at any fundamental frequency. Magnet segmentation is a common strategy to mitigate magnet losses. However, the effectiveness of loss reduction relies on many other factors, including electrical conductivity of the magnet, relative permeability, magnetic circuit, and winding distribution. Skin effect plays a significant role in loss reduction effects of PM under high frequency excitation. This has the possibility of reversing the expected loss reduction effects by segmentation, called anomaly of segmentation. This anomaly is investigated using analytical and FEA methods. Two similar sets of IPM and SPM rotors with different magnet segmentations are developed and used to experimentally validate the magnet eddy current loss trends. While the analytical loss models provide an accurate prediction of losses, they are driven by current excitation. An essential component of deciding the harmonic currents in a reactance limited circuit is the winding inductance, which is dependent on frequency and segmentation of the PM rotor. Therefore, an accurate way of predicting the inductance, voltage, and current harmonics for a VSI with space vector PWM is presented and validated with experimental results. Finally, a magnet loss reduction framework for various magnet loss components is proposed, aiming to encompass the broad set of variables that influence magnet eddy current losses and rotor temperature.

Graduation Semester

2023-12

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 Sirimanna Withanage Don Thusara Samith Sirimanna

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