Speed, flexibility, and precision: improving electrical machine production

The aerospace sector is increasingly focused on enhancing sustainability and efficiency to support a net-zero future. To achieve this, it is exploring various solutions, including the advancement of aero engine and component manufacturing.

To accomplish this, the sector must leverage on the latest advancements in electrical hybrid propulsion systems. With ongoing technological developments and improved efficiencies, there are growing opportunities to meet market demand and enhance supplier delivery.

AeroMC, (Aerospace Manufacturing Capability)Link opens in a new window is a 4.5 year £14m project funded by the Aerospace Technology Institute (ATI) which aims to address and invest in new research and manufacturing technologies that will achieve the maximum operational and economic exploitation for the aerospace sector, and a robust route to market for future products.

AeroMC is a consortium made up of Safran- the world’s second largest aircraft equipment manufacturer- and WMG and MTC (Manufacturing Technology Centre)- two members of the High Value Manufacturing Catapult (HVMC) network.

AeroMC will look to use the latest material and process advances in manufacturing automation to help transform the production of electrical machines. In parallel, the aim is to establish the Safran Electrical and Power (SEP) UK facility at Pitstone as a global centre of excellence for electrical Vertical Take-Off and Landing (eVTOL) and Hybrid Propulsion systems on new technology aircraft.

This was made possible by the state-of-the-art, laser beam welding facilities available at WMG, and the collaborative expertise and experience of multiple research groups. This approach enabled a number of technologies to be combined in an innovative way to facilitate not only automation of the manufacturing process but improvement in reliability and broadened the application options.

This solution, using remote laser beam welding in spot-welding mode, enables rapid assembly of stator windings and busbars. The method uses the magnet wire itself as filler material, ensuring an effective joint between the magnet wire and busbar-fork for a robust electrical and mechanical connection.

WMG conducted extensive testing and validation, exploring the impact of pre-welding surface conditions, misalignment tolerance, and welding parameters such as power, duty time and focal offset. The study also assessed the feasibility of sensor technology and machine learning methods for the classification of weld quality.

The new welding process demonstrated a number of significant key benefits:

Magnet Wire as Filler Material: Using the magnet wire itself as filler material effectively bridges the gap between the magnet wire and busbar, reducing the need for filler material, which reduces porosity, cost and process time. The laser welding approach achieved an efficient cycle time of ∼410 ms and produced a robust bonding across the entire busbar thickness, reaching 92.5% of the enamelled magnet wire’s load capacity, with failure occurring outside the welded region.

Low Thermal Damage: The welding process showed minimal thermal damage, which was a potential concern with the laser technique, with the magnet wire experiencing relatively higher temperatures than the busbar. Both remain well below the operational temperature limits of adjacent low-temperature components, such as the busbar carrier.

Minimal Pre-Welding Treatment and Tolerance to Pre-Treatment: The proposed welding approach requires minimal pre-welding surface treatment for the copper busbar. Even with prior treatments on the copper busbar, the method maintains strong mechanical, electrical and thermal performance, highlighting its high tolerance to differing surface conditions thereby creating a greater potential practical applicability for this technology.

In-Process System for Defect Classification: Machine learning-enabled photodiode sensor technology was used for weld morphology classification and welding parameter analysis, achieving up to 93.65% classification accuracy for specific scenarios. This presents opportunities for in-line quality assessment and significantly reduces reliance on the time- and cost- intensive experimental characterisation post welding.

Dr Sul Ademi, Lead Engineer for Electrical Machines at WMG, commented:

“Developing a practical and automated method of joining windings to a busbar is a real step forward in the manufacturing of electrical machines giving cost savings, improved reliability and control for repeatability. Critical to this development has been the collaboration between the Power Electronics and Electrical Machines, Laser Welding, Metrology groups and SEP. Although the focus of this project is aerospace, the joining method has wider applicability for machines destined for other sectors.”

Giovanni Raimondi, Machines & Drive Systems Technical Director, Safran Electrical & Power, stated:

“Working with WMG has been a fantastic experience for us at Safran. Without the expertise, facilities, sector experience and collaborative approach at WMG, laser welding was a form of automation we could not have explored. The results from this project are extremely promising, opening up many opportunities for SEP’s electrical machine manufacturing.”