The transition toward more sustainable aviation also relies, now more than ever, on propulsion systems. In this context, eVTOL (electric Vertical Take-Off and Landing) aircraft represent one of the most compelling technological developments of recent years: platforms designed to combine high performance, reliability, and reduced weight within fully electric architectures.
It is within this scenario that the study of a permanent magnet synchronous electric motor with an external rotor was developed, specifically designed for high-torque-density aerospace applications such as propulsion and propeller pitch control. Compared to traditional internal rotor configurations, this architecture delivers clear advantages:
The motor is designed as a 6-phase BLAC machine with concentrated windings and surface-mounted permanent magnets. The choice of a multiphase configuration is not only performance-driven, but also safety-oriented: in the event of a fault in one phase, the system can continue operating under controlled conditions, ensuring the electrical stability required in aerospace applications.
While the electromagnetic structure represents the core of the system, the real challenge lies elsewhere: thermal management.
Increasing power density inevitably requires handling higher levels of heat, and in the aerospace sector this directly impacts weight, complexity, and reliability.
For this reason, UMBRAGROUP’s engineering team set an ambitious goal: maximize performance without relying on centralized liquid cooling systems. The solution combines forced air cooling, an internally optimized heat exchanger designed through CFD simulations, and the integration of heat pipes within the stator slots. Heat pipes are passive devices with extremely high thermal conductivity, capable of transferring heat very efficiently through the evaporation and condensation of an internal fluid. This allows the system to operate without power supply or moving components.
The motor is not a standalone component, but part of a compact and fully integrated electromechanical system that includes propulsion, a Trim Pitch EMA (electromechanical actuator for propeller pitch control), and thermal management. This integrated approach reduces size and weight, simplifies the overall architecture, and facilitates onboard integration.
From a performance standpoint, the design achieves significant results:
The analyses performed also confirm stable behavior from both electromagnetic and thermal perspectives, even under the most demanding operating conditions.
This study demonstrates how high performance, reliability, and architectural simplicity can be effectively combined, paving the way for increasingly compact and efficient electric propulsion systems. In a sector where every kilogram and every degree matter, innovation also depends on thermal management.