A Doubly Fed Machine Using Magnetic Resonance Coupling and Air-gap Windings for High Power Density and Efficiency

Electric vehicles (EVs) and electric aircraft require motors with high power density and efficiency. This study proposes a doubly fed machine (DFM) featuring an air-gap winding (AGW) that operates under magnetic resonance coupling (MRC) to enhance power density and efficiency. The fundamental characteristics of the doubly fed magnetic resonance coupling machine (DF-MRCM) with AGW were analyzed revealing that its high output power results from an increased product of primary and secondary currents without magnetic saturation in the stator and rotor. The machine achieves high efficiency at elevated rotational speeds, attributed to reduced iron losses from MRC and a lightweight rotor constructed from high-strength carbon fiber-reinforced plastic. These design features enable the DF-MRCM with AGW to achieve a high power density of 9.7kW/kg at a high rotational speed of 39,960rpm, making it well-suited for EV and electric aircraft applications.