Operation Characteristics of a Magnetic Resonance Coupling Motor with a Magnetic Ring for 8 and 4 Poles

In this study, we describe and discuss the variable-speed characteristics of an ultralightweight motor based on magnetic resonance coupling (MRC) for the practical realization of electric aircraft. The MRC between the stator and rotor windings of a motor allowed wireless power transfer without a magnetic core. Thus, the coreless design made the motor substantially light with low iron core loss. We also describe the use of an MRC motor (MRCM) with a magnetic ring to enhance the torque and power and discuss the impacts of varying the number of 4 poles and 8 poles. We analyzed the MRCM with a thin magnetic ring via magnetic field analysis to demonstrate the power-density improvement and reveal the effects of the number of poles on the motor performance. Analytical results showed that the 4-pole motor had a power output of 1,200 kW at 100,000 rpm and a potential for a high-power density of 43.1 kW/kg. Also, the efficiency of the 4-pole MRCM was higher than that of the 8-pole MRCM.