EMRAX 228 axial-flux motor and generator

The EMRAX 228 is an axial-flux electric motor and generator from EMRAX d.o.o., a manufacturer based in Kamnik, Slovenia. It converts electrical energy to mechanical energy, or mechanical to electrical, and is used as a traction or propulsion machine in electric aircraft, hybrid-electric powertrains, vehicles and marine drives. The model designation carries its ratings: 124 kW peak power and 220 Nm peak torque.

The motor has a casing diameter of 228 mm and an axial length of 86 mm. Dry mass is 12.9 kg for the air-cooled version, 13.2 kg for the combined-cooling version and 13.5 kg for the liquid-cooled version. For a propulsion designer this flat, compact format and low mass allow a direct-drive arrangement on a propeller or fan, and the three cooling variants let the airframe thermal design choose between simple airflow and a liquid loop.

Peak power is 124 kW at 5500 RPM, and peak torque is 220 Nm. Continuous power reaches 75 kW and continuous torque 130 Nm, both subject to drive cycle, thermal conditions and controller capability. In practice the peak values define short take-off or climb phases, while the continuous values size cruise and sustained operation. Efficiency reaches 96 percent, which lowers the heat the cooling system must remove for a given shaft power.

Stator cooling is by air with an IP21 rating, by a combined method also at IP21, or by liquid at IP66. The motor is offered for maximum battery voltages of 830 V (HV), 630 V (MV) or 250 V (LV) DC, so the winding variant has to be matched to the battery and inverter architecture. Mounting uses six M8 threaded holes on the front and six on the back. EMRAX recommends motor controllers from partner suppliers, and two motors can be stacked to double power and torque on one shaft line.

EMRAX offers a technical data sheet, dimensional drawings, a 3D model and a manual for the motor, and states that further documentation can be provided during quotation and ordering. The company also describes its motors as EMC certified; no aviation airworthiness approval is stated on the product page.

Typical applications are electric and hybrid-electric aircraft propulsion, eVTOL and multirotor drives for larger platforms, series-hybrid generators, and ground and marine electric drivelines where high torque density and a compact axial dimension are needed.