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52 DESIGN007 MAGAZINE I JUNE 2025 Figure 3: Illustration of an electric motor's operation. Traditional radial flux and axial flux using PCBs 4 . Design AFMs can use single or dual rotors or stators. ey are com- mon in high-power applications, although they require a housing with accompanying iron losses. Single stator/dual rotor designs can dispense with the yoke, saving weight and increasing efficiency. In the latter, the rotors and their iron plates that close the flux move in the same direction/speed as the magnetic field. You can stack some AFMs to pro- vide higher power output in a mod- ular fashion. YASA's 37 kg stackable 750R motor delivers 800Nm and >5kW/kg with an axial length of 98 mm (3.9 in). Figure 5 shows an optimized coil pattern for axial-flux from soware like COMSOL Multiphysics elec- tric machine modeling, which supports axial, radial flux, and transverse flux motors. Soware is also available for axial flux motor designs from 4W to 20 kilowatts by ECM PCB Stator Inc. Aviation e Rolls-Royce Spirit of Innovation (holder of the current world speed record for an electric aircra) uses three axial flux motors. Mercedes- Benz subsidiary, YASA, makes AFMs for this plane. YASA's goal is to build aircra motors that deliver 50 kW/kg, to allow for the substan- tial weight reductions required for electric-pow- ered flight. A triple-stacked 200kW YASA 750R axial flux motor powers the 7.3 m (24 ) aircra, driving a 2,400 RPM, three-blade propeller. e 750 volt, 216 kWh battery has 6,480 cells, with cork insulation and active cool flux motor ng. Battery output power is continuous at 500 hp (373 kW), reaching 750 kW (1,010 hp) at maxi- mum power. e design aims to achieve the highest energy density for an aircra, enabling a 170 nautical mile range. (310 km). 5 Figure 4: The new axial flux motor with lightweight PCB stators replaces the traditional heavy iron core, copper windings of traditional motors used in HVAC and other power-consuming appliances 4 . 52 DESIGN007 MAGAZINE I JUNE 2025