Brody, Ryan
(2024)
Rare-Earth-Free Manganese Bismuth Permanent Magnet Synchronous Motor Design for Electric Vehicle Applications.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
This dissertation examines using Manganese Bismuth (MnBi) permanent magnets (PMs) in permanent magnet synchronous motors (PMSMs) for electric vehicle (EV) applications compared to popular commercially available alternatives, namely Neodymium Iron Boron (NdFeB) and ferrite PMs. MnBi has recently emerged as a promising rare-earth-free (RE-free) PM material, but until now, no group has designed a MnBi PMSM suitable for EV applications, which typically require large quantities of rare-earth PMs with high, volatile cost. Three research Objectives explore this topic, serving as foundational work for MnBi PMSMs at the power, torque, speed, and current ratings required for EV drivetrains.
Objective 1 presents a trade study for MnBi interior permanent magnet synchronous motors (IPMSMs) using a topology commonly found in EVs today. The study is based on an exemplary design from industry that is well documented in literature: the motor design first used in the 2011 Nissan Leaf, also used in the 2012 Nissan Leaf. Objective 1 confirms trends in literature for other PM materials which suggested that MnBi IPMSMs will suffer from low power factor and low constant power speed ratio (CPSR) compared to a similar NdFeB IPMSM because MnBi has a lower remanent flux density (B_r) than NdFeB.
Therefore, Objective 2 presents a trade study for a MnBi permanent magnet assisted synchronous reluctance motor (PMASynRM) topology that is better suited for RE-free PMSMs in some applications than the IPMSM topology. Comparing the MnBi IPMSM and MnBi PMASynRM reveals tradeoffs between torque density, temperature-dependent irreversible demagnetization, mechanical rotor stress, power factor, and CPSR.
These tradeoffs occur because MnBi PMs are significantly more susceptible to irreversible demagnetization at low temperatures, since coercivity (H_c) significantly increases with increasing temperature. To enable competitive MnBi PMSM designs despite demagnetization risk, Objective 3 presents an observer capable of estimating magnet temperature with fast convergence compared to other options in literature. This will help to predict irreversible demagnetization risk at low temperatures during motor startup in EVs.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
3 June 2024 |
| Date Type: |
Publication |
| Defense Date: |
12 March 2024 |
| Approval Date: |
3 June 2024 |
| Submission Date: |
29 February 2024 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
182 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Electrical and Computer Engineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Electric Transportation, Interior Permanent Magnet Synchronous Motor, Permanent Magnet Synchronous Reluctance Motor, Manganese Bismuth (MnBi), Motor Design, Multi-Objective Optimization, Trade Study, Rare Earth (RE) Free, Neodymium Iron Boron (NdFeB), Constant Power Speed Ratio, Flux Weakening, Irreversible Demagnetization, Reduced Order Model, Meta-Model, Short Circuit Current, |
| Date Deposited: |
03 Jun 2024 14:38 |
| Last Modified: |
03 Jun 2024 14:38 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/45827 |
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