Mechanical and Vibration Analysis of a High-Speed Outer Rotor Electric Motor

Abstract

This study explores the design and engineering of high-speed outer rotor electric motors, focusing on addressing the unique challenges these motors face for integrated drive applications. Outer rotor motors are preferred in applications requiring high power density and compact design. They enable efficient use of space by integrating power electronics within the motor structure, a critical advantage over traditional inner rotor designs. However, the adoption of high-speed outer rotor motors introduces several technical challenges, including managing increased mechanical stresses, ensuring dynamic balance, mitigating vibrations, and the need for specialized bearings capable of supporting high operational speeds. To tackle these issues, the study proposes a novel design framework that includes two configurations: a cantilevered design and a design supported at both ends. A significant innovation within this framework is the use of a C-fiber-based sleeve around the rotor. This sleeve preloads the magnets and the rotor structure, enhancing the motor’s mechanical integrity and allowing it to operate safely at speeds up to 20,000 rpm. The study employs finite element analysis for structural and modal assessments alongside rotodynamic studies to evaluate the proposed designs. These analyses are crucial for understanding the vibrational behavior and stability of the motor under operational conditions. Based on these evaluations, the study presents specific recommendations to improve the rotodynamic performance of the motors, focusing on aspects such as balancing and vibration reduction.

Keywords

• Electric motor
• natural frequency
• permanent magnet
• rotodynamic
• spin analysis