EMRAX 348 axial-flux motor and generator

The EMRAX 348 is an axial-flux synchronous motor and generator from EMRAX, designed as a compact electric traction or generator machine for aircraft, vehicles and marine drives. It converts electrical energy to mechanical energy, or the reverse when used as a generator, and it is offered in air-cooled, combined-cooled and liquid-cooled versions.

The key figures describe a high-torque machine in a short package. The casing is 348 mm in diameter and 112 mm long in the axial direction. Peak power is 340 kW at 4000 RPM and continuous power is up to 180 kW, depending on the drive cycle, thermal conditions and the capability of the controller. Peak torque is 1000 Nm and continuous torque is up to 396 Nm. Peak efficiency is up to 96 percent. For a propulsion designer the peak values set the short-duration take-off or climb capability, while the continuous values determine what the cooling system must sustain in cruise.

Dry mass depends on the cooling variant: 43.1 kg for the air-cooled version (AC), 43.5 kg for the combined-cooled version (CC) and 43.9 kg for the liquid-cooled version (LC). The air-cooled and combined versions are rated IP21, and the liquid-cooled version IP66. Choosing between them is a trade-off between the simplicity of airflow cooling and the higher sustained output and ingress protection of a liquid loop, which also needs a pump, radiator and coolant routing in the airframe.

Electrical integration is by a three-phase motor controller matched to the machine. The maximum battery voltage is 830 Vdc for the high-voltage and medium-voltage versions and 600 Vdc for the low-voltage version, so the winding version has to be selected to suit the traction battery or DC bus of the aircraft. The controller, its current capability and the thermal arrangement all limit the power that can actually be used.

Mechanical installation uses six M12 threaded holes on the front face and ten M8 threaded holes on the back face. Two motors can be stacked on a common shaft to double the available power and torque, which allows one motor family to cover distributed-propulsion layouts and larger single-propeller drives.

The motor is used as a direct or geared propulsion drive in light aircraft, hybrid-electric and fully electric aircraft and eVTOL concepts, as well as in automotive and marine drivetrains, and as a generator in range-extender systems.