A wide range of requirements are made on the windings of electric motors. On the one hand, the optimal use must be made of the available installation space by using a high slot-filling ratio. On the other hand, the best possible cooling of the conductors must be assured, and additional efficiency reductions caused by a current displacement should be avoided. Moreover, production and assembly of the coil should be cost-effective and automatable.

Fraunhofer IFAM has developed a method that allows coils for electric motors to be produced by casting. The coil geometries produced, which use a flat conductor arrangement (Fig. 1), offer significant benefits in all the above-mentioned aspects compared with conventionally produced windings.

Filling factors of up to 90 per cent
The geometric degrees of freedom that production by casting offers enable the conductor cross-section to be specifically adapted to the installation space available. The complete utilization of the slot cross-section of electric motors allows filling factors of up to 90 per cent to be achieved (Fig. 2). Another advantage of this method of production is that the bending radii at the winding head, necessary in wound coils, can be eliminated, allowing conductor length and axial installation space to be reduced. Consequently, electric resistance is reduced by up to 50 per cent compared with that of a wound coil in the same installation space

Ideal thermal and electromagnetic properties 
Apart from the high filling factor, the flat conductor arrangement offers furtheradvantages from an electromagnetic and thermal point of view. Compared with a wound wire with the same cross-sectional
area, thermal behavior is significantly improved while the negative influence of the skin effect is minimized. This allows continuous current densities of between 18 and 24 A/mm² to be achieved, depending on
the coil size (Fig. 3). As a result, the current density in the slot can be tripled compared with that of conventionally produced coils. 铸件展-铸件采购会-国际铸件展-2020第二十一届广州国际铸件展会-巨浪展览 -The 21st China (Guangzhou ) Int’l Casting product Exhibition -Casting product Exhibition, 2020 casting product Exhibition, China Casting product Exhibition, Casting Exhibition, China Casting Exhibition, 2020 Casting Exhibition, Casting product Expo, 2020 casting product Expo, China Casting product Expo, Casting Expo, China Casting Expo, 2020 Casting Expo,