Comparison of synchronous motors for hybrid light aircraft with conventional and additive winding technologies
Electric motors are key components for the electrification of aviation. This is of significant importance for the industry.
Aircraft already use electric motors for primary and secondary surface controls, for the landing gear and for other operations such as high-lift systems. Future aircraft and drones will require powerful electric motors for propulsion.
The motors present a major challenge due to the high power density required. Hybrid-electric propulsion is one of the most important topics in the aviation industry and offers the opportunity to drive forward the change towards electrification, especially in the light aircraft segment.
Together with the Umbra Group, we compared permanent magnet synchronous motors for the propulsion of hybrid light aircraft with traditional and additive winding technologies in a development project.
The design of the electric motors was adapted in terms of the electromagnetic design and the winding. Based on the original design, the active materials and motor typology (i.e. permanently excited synchronous motor) were retained, which is one of the most commonly used for drive applications. In addition, various thermal simulations were carried out and improvements made to the cooling circuits.
The project compared two electric motor designs with different winding technologies to investigate the use of additive manufacturing and 3D printing in winding production. Both designs have some similarities that correspond to the design-to-cost approach (e.g. stator laminations, housing, rotor, magnets). The optimisation of the 3D-printed windings was mainly focused on the shape and arrangement of the conductors in the slot to minimise AC losses.
One of the main advantages of flat conductor winding over round wire winding is the higher copper fill factor. Random windings, as are common with round wires, have a maximum copper fill factor of about 45%, whereas flat conductors achieve a maximum slot fill factor of about 80%.
A higher fill factor naturally means a larger copper cross-section in the same slot, which leads to a lower current density, lower DC resistance and thus to lower power losses and higher efficiency.
3D printing was able to demonstrate several strengths in this project:
- no design restrictions
- integration of the busbar into the winding – no additional welding required
- less stress on the copper conductors and insulation, as no bending is required
Another advantage of additive manufacturing is the enormous cost savings in the development of prototypes, since, in contrast to conventional processes, no tools and no production plant set-up are required.rototypes, as unlike conventional processes, no tools and no set-up of the production plant are required.
Giovanni Di Domenico – Umbra : “One advantage of the stator with additive manufacturing is the compactness of the end winding on connection side in comparison to the one with traditional winding technology. This aspect is very important and ensure to reach a higher power density and lower envelopes with a redesign.”
