Prototype fabrication of complex cooling channels by potting, additively manufactured inserts in an electric motor

Embedding additively manufactured tube structures into the resin encapsulation of high-power electrical devices promises great theoretical benefits for increasing heat dissipation and thus power density. In the considered project, channels were integrated into the potting of a slot-cooled electric motor to enable a three-dimensional coolant flow at the winding head. The thin-walled insert consisting of 34 channels in a ring structure with closed endcaps was manufactured using the additive LPBF process. In this context, various support structures were tested and evaluated in advance with regard to their suitability for process-stable separation of the printed component from the build platform. The insert investigated was then printed from steel metal powder with linear support structures. The separation from the build platform took place by circular milling using a specially developed clamping system. The cooling channels were then opened by drilling through existing cooling channels in the resin. The trapped metal powder inside is removed and investigated for recyclability. The potting of the motor windings is done with a polyurethan resin with fillers to enhance the thermal conductivity. As the water-based coolant is directly in touch with the potting material, properties as the permeability to water due to cracks or gas bubbles and O-ring sealing interface behavior were considered in the material selection. The vacuum potting process was done in a throw flow potting tool.