1. Technical characteristics of eVTOL motor
In distributed electric propulsion, motors drive multiple propellers or fans on the wings or fuselage to form a propulsion system that provides thrust to the aircraft. The power density of the motor directly affects the payload capacity of the aircraft. The power output capacity, reliability and environmental adaptability of the motor are important factors to determine the dynamic characteristics and safety of the electric propelled aircraft. The selection of electric vehicles, drones and eVTOL motors is different due to different costs, application scenarios and other reasons [1].
(Photo source: Network/Safran official website)
1) Electric vehicles: more permanent magnet synchronous motors, permanent magnet motors with higher efficiency and higher torque can provide a better driving experience. At the same time, the high power density of permanent magnet motors can also help electric vehicles obtain higher power under the same volume.
(2) UAV: commonly used brushless DC motor. The brushless DC motor has low weight and noise, and the maintenance cost is low, which is suitable for the flight requirements of UAVs; Second, the speed of the brushless DC motor is higher, which is suitable for the high-speed flight needs of drones. For example, DJI uses brushless motors.
(3) eVTOL: Higher requirements for motor efficiency and torque density, permanent magnet synchronous motor is a very promising solution for electric propulsion power system, because the axial flux permanent magnet motor has a high utilization rate of radial space, and the power density and torque density have advantages in the case of small length diameter ratio. Current electric VTOL aircraft, such as Joby S4 and Archer Midnight, all adopt permanent magnet synchronous motors [1].
The following figure shows the cloud image of fixed rotor magnetic induction intensity of single-stator single-rotor axial flux motor
The following figure is a comparison of electric aircraft and electric vehicle motor parameters
2.eVTOL motor development trend
At present, the main development trend of eVTOL power system is to reduce the weight of the motor structure and the auxiliary weight of the cooling system by improving the electromagnetic design technology, thermal management technology and lightweight technology, and constantly improve the power density of the motor and the power output capacity of a wide range of variable conditions. According to the “Research and Development of Flying cars and Key Technologies”, the aviation propulsion motor has been able to make the rated power density of the motor body more than 5kW/kg by using insulation materials with higher temperature limits, permanent magnet materials with higher magnetic energy density and lighter structural materials. By improving the electromagnetic structure design of the motor, such as the use of Halbach magnetic array, no iron core structure, Litz wire winding and other technologies, as well as improving the heat dissipation design of the motor, it is expected that the rated power density of the motor body can reach 10kW/kg in 2030, and the rated power density will exceed 13kW/kg in 2035 [1].
3. Comparison of pure electric and hybrid routes
Compared with the pure electric route and the hybrid route, from the current selection of relevant manufacturers, the domestic eVTOL project is mainly based on the pure electric scheme, limited by the energy density of lithium-ion batteries, and the low-passenger capacity eVTOL is the best landing scene of pure electric propulsion technology. Overseas, some manufacturers have laid out the hybrid plan in advance, and have taken the lead in multiple rounds of testing and iteration. As can be seen from the following table, the hybrid scheme is obviously stronger in the endurance Angle, and can achieve more applications in the scenario of middle-long distance and low altitude traffic in the future [1].
Post time: Feb-27-2025