Die-cast Aluminum Coils For More Efficient Electric Motors

2023 Author : Hannah Pearcy | [email protected] . Last modified: 2023-06-05 00:21

Whether pedelecs, e-scooters or drones - all of these forms of mobility have an electric motor. The motors are identical in construction and have a rotor that is wrapped with a copper wire. In order to make the engines more efficient, the focus is on questions of efficiency, weight, material and manufacturing costs.

Coils for series production also in die casting

After it had already been possible to manufacture aluminum coils in investment casting in the past few years, it was an obvious goal of the "Foundry Technology and Lightweight Construction" department at the Fraunhofer Institute for Manufacturing Technology and Applied Materials Research IFAM to manufacture the coils for series production also in die casting.

Cast coils are characterized by a flat conductor arrangement, which leads to a higher slot filling factor and thus to a better use of the available space. Although the cast aluminum coils have a higher electrical resistance in relation to the material than the wound copper coils, the larger cross section results in a lower resistance in relation to the entire coil.

Better thermal and electromagnetic behavior

According to the institute, the better connection to the laminated core and cheaper use of the installation space results in better thermal and electromagnetic behavior. For this reason, it is possible to replace wound copper coils with cast aluminum coils with improved performance and lower material costs. In order for the proof to be successful in a direct comparison, commercial pedelec motors with 250 W were used for the study. The converted motors with different laminated cores and coil combinations were then tested on a test bench.

Aluminum coils improve efficiency

After the conversion of the Pedelec motor, the groove fill factor could be increased from 32% to 60% according to the institute. At the same time, there was a weight saving of 10%. The torque increased by 30%. Due to the better thermal behavior of the coils, the continuous power at operating temperature is said to have increased by almost 20%. The aluminum coil can better transfer the heat generated to the laminated core and thus to the environment. This results in an improved continuous output, since the coils only reach the permissible continuous operating temperature at higher currents.

The measurement results were even more advantageous with a laminated core optimized for the cast coils for another modified pedelec motor. With less weight, the torque increased by almost 80% and the continuous output by 25% compared to the original engine. Design changes should further increase the performance of motors with aluminum coils.

Potential for electric motors of different products

Thanks to the many years of development work on cast coils at Fraunhofer IFAM, it is now possible to cover a wide variety of application scenarios. For use in high-performance machines, copper coils of the highest quality can be produced in investment casting. For use in series production, as z. B. in the manufacture of steering motors or refrigeration and air conditioning systems, according to the institute, the die casting process is particularly suitable. In order to optimize die casting production and further reduce manufacturing costs, the next development step is the automated reworking of the coils. According to the institute, large quantities in short cycle times can then be manufactured in every die-casting foundry.

Fraunhofer IFAM at Euroguss 2020: Hall 7, Stand 422

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