When plastics are used in electric components, the selection process examines mechanical properties, temperature capability, flammability, thermal conductivity, and moldability, as well as the need for electrical resistance to isolate the system for safety reasons. Though good electric insulators, plastics are poor conductors of heat when compared to metals. Losses in electric motors due to windage, friction, winding, or iron will manifest as undesirable heat build-up, raising the temperature inside the motor. The choice of materials for both high thermal conduction and electrical isolation, therefore, directly impacts motor performance.
This Tech Talk looks at the work being done in developing thermally conductive electrically insulated (TCEI) materials for e-motor applications. Fillers play an important role in material properties of plastics, and new grades of TCIE materials have been developed that demonstrate improved conductivity over commercially available choices. The thermal conductivity of these novel materials have been quantified using a unique finite-element model for bobbins, which captures the effect of material choice on temperatures within the system. The model incorporates material orientation within the bobbin and also evaluates the effect of the air gap between the bobbin and the laminated core. Results show that materials with improved thermal conductivity have reduced bobbin and winding temperatures, offering significant performance benefits.