As the drone industry expands rapidly, the demand for high-performance propulsion systems with high power density, superior energy efficiency, and lightweight characteristics has grown significantly. Outer-rotor permanent magnet synchronous motors (OR-PMSMs) are particularly well-suited for drone propulsion, due to their superior torque density and efficient thermal management, compared to inner-rotor structures. However, achieving accurate performance prediction during the initial design phase remains challenging due to complex electromagnetic phenomena. This paper proposes an analytical methodology using the subdomain method to evaluate the electromagnetic performance of OR-PMSMs, specifically accounting for slotting effects caused by stator geometry. Rather than focusing on complex optimization algorithms, this study prioritizes comprehensive performance evaluation and experimental validation. Key electromagnetic parameters and circuit constants—including air-gap flux density, back-EMF, winding resistance, inductance, and electromagnetic torque—are calculated efficiently using the proposed analytical model. To complement the limitations of analytical formulation regarding core saturation and flux leakage, the finite element method (FEM) is conducted for comparative evaluation. Furthermore, a physical prototype of the OR-PMSMs for drone propulsion was fabricated, and experimental tests were performed to validate the analytical and numerical results. The analytical predictions demonstrate strong agreement with both the FEM simulations and experimental measurements, confirming the accuracy and reliability of the proposed framework. Consequently, this study addresses the inherent constraints of conventional analytical methods and provides a computationally efficient, yet precise, evaluation procedure, serving as valuable baseline data for the design and development of high-efficiency, lightweight drone propulsion motors.

An interior permanent magnet synchronous motor (IPMSM) rotor equipped with a carbon-fiber-reinforced plastic (CFRP) sleeve, based on an electromagnetic–mechanical coupled analysis approach, was designed and analyzed. As the demand for high-speed traction motors increases, addressing the excessive rotor stress caused by higher rotational speeds has become critical. To mitigate this issue, a CFRP sleeve is used to enhance mechanical strength while minimizing the impact on electromagnetic performance. However, the introduction of the CFRP sleeve increases design complexity because of changes in air gap length and structural constraints. The crucial considerations required in the design and manufacturing processes, including tradeoffs between mechanical integrity and magnetic performance, are discussed. The proposed design methodology differentiates the rotor structure from conventional IPMSMs, offering a viable solution for high-speed, high-power-density motor applications.

This paper proposes a pulse width modulation (PWM) switching sequence strategy aimed at minimizing common-mode voltage (CMV) in three-phase motor drive systems. CMV, originating from the charging and discharging of parasitic capacitances, can lead to issues such as electromagnetic interference (EMI) and premature bearing failure. While conventional reduced CMV-PWM (RCMV-PWM) techniques address these problems, they are limited by CMV spikes that diminish their effectiveness. This paper introduces an improved switching sequence that mitigates CMV spikes across all motor operating regions. The proposed method is developed by analyzing CMV variations and identifying the causes of spikes in active zero state PWM (AZSPWM) techniques. Its effectiveness is verified through both simulation and experimental validation against standard space vector PWM (SVPWM) and conventional AZSPWM.