Demagnetization prevention using optimization of PM machine operation with integrated multi speed transmission.

Area of Science:

• Electrical Engineering
• Mechanical Engineering
• Materials Science

Background:

• Permanent magnet (PM) machines in electric vehicles (EVs) face operational challenges, including irreversible demagnetization under wide speed ranges and high temperatures.
• The field weakening region poses a significant risk to PM machine integrity and longevity in EV powertrains.

Purpose of the Study:

• To develop and validate a methodology for optimizing electric bike powertrains to mitigate PM machine demagnetization.
• To investigate the effectiveness of a multi-speed transmission (MST) system in enhancing the reliability of PM machines in EVs.

Main Methods:

• Joint optimization of PM machine design parameters and multi-speed transmission (MST) gear ratios.
• Confining machine operation to targeted speed and torque intervals using the MST system.
• Comparative analysis of system reliability and energy efficiency under various driving conditions, including the WLTP Class 3 drive cycle.

Main Results:

• The adoption of MST architecture significantly reduces time spent in the field weakening region from 57% to 10%.
• Energy assessments indicate that additional losses from gearbox weight are dependent on the drive cycle and driver behavior.
• The proposed methodology effectively suppresses demagnetization phenomena, enhancing system reliability.

Conclusions:

• The holistic powertrain design approach, integrating MST, offers a viable solution to prolong the service life and economic viability of PM machines in EV applications.
• Optimized powertrain design is crucial for addressing operational challenges and ensuring the long-term performance of electric vehicle components.